METHOD: Hydrazinyl thiazole substituted coumarins 4-20 were synthesized via two step reaction. First step was the acid catalyzed reaction of 3-formyl/acetyl coumarin derivatives with thiosemicarbazide to form thiosemicarbazone intermediates 1-3, followed by the reaction with different phenacyl bromides to afford products 4-20. All the synthetic analogs 4-20 were characterized by different spectroscopic techniques such as EI-MS, HREI-MS, 1H-NMR and 13C-NMR. Stereochemical assignment of the iminic double bond was carried out by the NOESY experiments. Elemental analysis was found in agreement with the calculated values.
RESULTS: Compounds 4-20 were screened for α-amylase inhibitory activity and showed good activity in the range of IC50 = 1.829 ± 0.102-3.37 ± 0.17 µM as compared to standard acarbose (IC50 = 1.819 ± 0.19 µM). Compounds were also investigated for their DPPH and ABTS radical scavenging activities and displayed good radical scavenging potential. In addition to that molecular modelling study was conducted on all compounds to investigate the interaction details of compounds 4- 20 (ligands) with active site (receptor) of enzyme.
CONCLUSION: The newly identified hybrid class may serve as potential lead candidates for the management of diabetes mellitus.
METHODOLOGY/PRINCIPAL FINDINGS: The in vitro study demonstrated that T. indica fruit pulp had significant amount of phenolic (244.9 ± 10.1 mg GAE/extract) and flavonoid (93.9 ± 2.6 mg RE/g extract) content and possessed antioxidant activities. In the in vivo study, hamsters fed with high-cholesterol diet for ten weeks showed elevated serum triglyceride, total cholesterol, HDL-C and LDL-C levels. Administration of T. indica fruit pulp to hypercholesterolaemic hamsters significantly lowered serum triglyceride, total cholesterol and LDL-C levels but had no effect on the HDL-C level. The lipid-lowering effect was accompanied with significant increase in the expression of Apo A1, Abcg5 and LDL receptor genes and significant decrease in the expression of HMG-CoA reductase and Mtp genes. Administration of T. indica fruit pulp to hypercholesterolaemic hamsters also protected against oxidative damage by increasing hepatic antioxidant enzymes, antioxidant activities and preventing hepatic lipid peroxidation.
CONCLUSION/SIGNIFICANCE: It is postulated that tamarind fruit pulp exerts its hypocholesterolaemic effect by increasing cholesterol efflux, enhancing LDL-C uptake and clearance, suppressing triglyceride accumulation and inhibiting cholesterol biosynthesis. T. indica fruit pulp has potential antioxidative effects and is potentially protective against diet-induced hypercholesterolaemia.